Publication Summary
Issue ID: GBCR2008-01-09
Title: Geological Setting of Volcanogenic Massive Sulphide Occurrences in the Middle Paleozoic Sicker Group of the Cowichan Lake Uplift, Southern Vancouver Island, British Columbia
Author(s): Ruks, T., Mortensen, J.K.
Series Name: Geoscience BC Report
Publication Year: 2008
Larger Work Citation: in Geoscience BC Report 2008-1
NTS Map Sheet(s): 092F/02,07
Place Keyword(s): British Columbia, Vancouver Island, Sicker Group
Lat/Long (NSWE): 50, 49, -126, -124
Theme Keyword(s): VMS deposits, Stratigraphy, U-Pb zircon geochronology, lithogeochemistry, Paleozoic
Additional Link(s):
Volcanogenic strata of the mid-Paleozoic Sicker Group on Vancouver Island occurs in several distinct basement highs (referred to as ‘uplifts’ herein). These rocks host the world-class Myra Falls volcanogenic massive sulphide (VMS) deposit (combined production and proven and probable reserves in excess of 30 million tonnes of Zn-Cu-(Au-Ag) ore), as well as numerous other VMS deposits and occurrences, especially in the Big Sicker Mountain area in the southeastern part of the Cowichan Lake up lift. Geological mapping suggests that the geology of the Mount Sicker area consists mainly of deformed mafic to felsic volcanic and volcaniclastic rocks of the Nitinat and McLaughlin Ridge formations, and high-level intrusions of the Saltspring intrusive suite, as well as abundant gabbroic dikes and sills of the Triassic Mount Hall gabbro. Geological mapping in the Cowichan Lake up lift of the Port Alberni area indicates that this area is largely underlain by basalt to basaltic-andesite volcanic rocks of the Duck Lake and Nitinat formations, respectively, in addition to felsic tuffaceous volcaniclastic rocks be longing to the McLaughlin Ridge Formation. The nature of the McLaughlin Ridge Formation rocks in the Port Alberni area is interpreted to represent deposition distal from a volcanic centre, which is thought to be represented in the Saltspring Island–Cowichan Lake area by felsic intrusive rocks of the Saltspring intrusive suite. Both reconnaissance and detailed geological mapping, together with sampling for lithogeochemistry, U-Pb zircon dating, and Nd, Hf and Pb isotopic studies, were conducted over a 20-day period in the Port Alberni area in October 2007. This work was concentrated in the vicinity of the Debbie 3 VMS occurrence and the area of potentially correlative exhalative iron formations to the west. This report presents a preliminary version of revised geological mapping in this area, with emphasis on understanding the geology in the vicinity of the Debbie 3 VMS occurrence and the potentially correlative Lacy and Esary Lake exhalative iron formations.